The present disclosure relates to a substrate processing apparatus, and more particularly, to a substrate processing apparatus that is capable of improving process uniformity on an entire surface of a substrate.
In general, substrate processing apparatuses are classified into single wafer type substrate processing apparatuses capable of processing one substrate and batch type substrate processing apparatuses capable of processing a plurality of substrates at the same time. Such a single wafer type substrate processing apparatus has a simple structure, but has low productivity. Thus, the batch type substrate processing apparatuses capable of being mass-producing substrates are being widely used.
A substrate processing apparatus may perform a substrate processing process on one or plural substrates at an increased temperature. In such a batch type substrate processing apparatus in which a plurality of substrates are loaded in multi stages, it is necessary to uniformly heat the vertically stacked substrates so that the processing process is uniformly performed on all the substrates. Since a heating unit uniformly heats the entire region at the outside of a reaction tube in the typical substrate processing apparatus, each of upper and lower portions may have a temperature less than that of an intermediate portion due to a difference in temperature between the upper and lower portions and the surrounding portion.
To solve this limitation, a method in which the heating unit may be divided in multi stages to separately control each stage is being used.
Although the above-described method is capable of solving non-uniformity of the substrates, it may be difficult to improve uniformity on an entire surface of each of the substrates. To improve the uniformity on the entire surface of the substrate, it is important to control a temperature of the heating unit. However, the typical substrate processing apparatus uses a method in which the heating unit uniformly heats the circumference of the reaction tube. In this method, a temperature in an injection nozzle region may be different from those in other regions due to the influence of a process gas temperature to cause non-uniformity in the processing process. When the reaction tube has a uniform temperature in the entire inner region thereof, a gas partial pressure in the injection nozzle region may be relatively high to cause a limitation in which a portion of the substrate approaching an injection nozzle is more processed than other portions of the substrate (e.g., a layer grown on the portion of the substrate approaching the injection nozzle has a relatively thick thickness).